The invention relates to a reversible cutting plate made from ceramic material for chucking in a cutting tool for machining cast materials.
A reversible cutting plate made from ceramic material for chucking in a cutting tool for machining cast materials, in particular cast iron, is known from EP 0 075 177. On its surface, the cutting plate contains a star-shaped depression with four points for the engagement of a chucking claw or a clamping finger of the cutting tool, with each corner of the reversible cutting plate having a minor cutting edge and a major cutting edge.
The cutting tool accordingly consists of a clamping holder and an exchangeable cutting plate that is to be inserted into the clamping holder. The cutting plate is that part which acts on the work piece and machines the latter. The cutting plate must therefore be made from an extremely hard material which abrades to a minimum extent when machining metal work pieces.
Materials that satisfy these requirements are oxide-ceramic materials, such as, for example, aluminium oxide or zirconium oxide. Such ceramic materials have a very high level of hardness and pressure resistance, yet only limited tensile strength.
The underlying object of the invention is to improve a reversible cutting plate in such a way that shavings from the cast-material are removed from the cutting edge and, as a result, the cutting edge is relieved.
In accordance with the invention, this object is achieved by grinding, pressing or injecting the corners into approximately xc2xc of the diagonal plane and thus forming a triangular face or shaving-forming shoulder and the triangular face having at least one incline. As a result, the shavings of cast material are removed from the cutting-edge corner towards the centre of the cutting plate and thereby relieve the cutting edge. A positive shaving-forming shoulder is created by means of these measures.
In a preferred embodiment, the triangular face is inclined at an angle a from the minor cutting edge in the direction of the side centre.
An alternative embodiment is characterised in that the triangular face is divided into two partial faces by the diagonal and at least one partial face is inclined from the major cutting edge or the minor cutting edge respectively at right angles, at an angle a towards the centre of symmetry. Advantageously, both partial faces are inclined towards the centre of symmetry. The centre of symmetry is understood as the point of intersection of the diagonals of the cutting plate with the hypotenuse of the triangular face.
The angle xcex1 preferably lies between 3 and 12xc2x0. For example, with a plate thickness d of 5 mm, a preferred maximum drop x of 1.5 mm results.
In accordance with the invention, the minor cutting edges are preferably provided with a planar supporting surface at their outer edge, which planar supporting surface, when the cutting plate is turned, relieves the major cutting edge located on the other side.
A significant feature of the invention is that the cutting plate is formed as a reversible cutting plate, with the minor cutting edges and major cutting edges being arranged on the two sides in such a way that they are offset by 90xc2x0 in each case so that one major cutting edge on the one side lies opposite one minor cutting edge on the other side and vice versa. As a result of the planar supporting surface along the minor cutting edge, the major cutting edge is thus supported on the other side. The planar supporting surface preferably extends over the entire length of the minor cutting edge and is of a width of preferably 1 mm.
Each corner is subdivided into two triangles by the associated diagonal. In the plan view of an upper side, viewed in the clockwise direction, the major cutting edge is arranged in front of the diagonal and the minor cutting edge is arranged behind the diagonal. This applies to cutting plates that rotate from left to right. For cutting plates that rotate from right to left, it is the reverse.
In one preferred embodiment the cutting plate has, for the purpose of securing the cutting plate in the cutting tool, a star-shaped depression with four points, with the points each being aligned with respect to the centre of one longitudinal side. A clamping finger of a chucking claw of the cutting tool engages into the depression in such a way that it is fixed in its position.
In accordance with the invention, all four corners of an upper side of the cutting plate can be used for cutting purposes. An identical depression is arranged on the rear side of the cutting plate so that eight corners are available in all for cutting purposes.
In an alternative embodiment, a hole is arranged in the cutting plate for the engagement of a gripping bolt of the cutting tool instead of the depression.
Apart from the corners which are formed in accordance with the invention, the reversible cutting plate can also have a smooth surface. These cutting plates are also termed smooth cutting plates.